The present invention relates to telecommunication networks and, more particularly, to traffic engineering in a telecommunication network.
Packet-switched networks, such as networks utilizing the TCP/IP protocol suite, typically rely on a store-and-forward paradigm and shortest-path routing protocols that do not take into account network parameters such as traffic demands and resource utilization. Traffic engineering (“TE”) is directed to optimizing such performance parameters in an operational network. Recent proposals have focused on using Multiprotocol Label Switching (“MPLS”) to force traffic onto specific label switched paths, thereby permitting network operators to automatically redistribute packet flows in some fashion that maximizes utilization of network resources. See, e.g., D. Awduche et al., “Requirements for Traffic Engineering Over MPLS,” Internet Engineering Task Force (IETF), Network Working Group, Request for Comments (RFC) 2702, September 1999; E. Rosen et al., “Multiprotocol Label Switching Architecture,” IETF Network Working Group, RFC 3031, January 2001. An MPLS TE tunnel/trunk is essentially a connection-oriented entity on top of the conventional connectionless IP network. Given a set of traffic engineering constraints, a label switched path (LSP) is determined by a constrained shortest path first (CSPF) algorithm. The explicit route output by CSPF is then dynamically setup by a signaling protocol, e.g. RSVP or CR-LDP. See D. Awduche et al., “RSVP-TE: Extensions to RSVP for LSP Tunnels,” IETF Network Working Group, RFC 3209, December 2001; B. Jamoussi, ed., et al, “Constraint-Based LSP Setup using LDP,” IETF Network Working Group, RFC 3212, January 2002.
Despite the potential benefits of deploying TE tunnels in IP networks, there are also concerns as well about its scalability and complexity to network operation. Moreover, at present, its admission control mechanisms are only applied at the tunnel setup time—not at the packet forwarding time. Thus, traffic inside a tunnel has to compete for the same bandwidth with traffic in another tunnel and regular IP traffic not carried by any tunnels. A group within the Internet Engineering Task Force is actively attempting to define traffic engineering in the context of what are referred to in the art as “Diff-Serv” mechanisms, to permit the enforcement of different bandwidth constraints for different classes of traffic. See F. Le Faucheur, ed., et al., “Requirements for support of Diff-Serv-aware MPLS Traffic Engineering,” IETF Network Working Group, Internet Draft, draft-ieff-tewg-diff-te-reqts-05, June 2002; F. Le Faucheur, ed., et al., “Protocol extensions for support of Diff-Serv-aware MPLS Traffic Engineering,” IETF Network Working Group, Internet Draft, draft-ietf-tewg-diff-te-proto-01, June 2002. Unfortunately, Diff-Serv-aware TE would have very complicated configuration requirements and also would require separate provisioning of queues in each router. A sophisticated bandwidth broker operation support system would also be needed for DS- TE to coordinate queue bandwidth and RSVP bandwidth.